1. Field of the Invention
The present invention relates to equipment for use with a three-phase alternating current (AC) power distribution system. In particular, the present invention relates to a power connector that is suitable for connecting a three-phase power supply to equipment using internally one or more single-phase voltages.
2. Discussion of the Related Art
Three-phase power is frequently used in high-power systems or equipment as the input power. Within each equipment or system, however, the three-phase power is almost always converted into a single phase through a redistribution operation. Because the specification for three-phase power is different in different countries, the input connection of the equipment to the three-phase power supply depends upon the country in which the equipment is to be used. FIGS. 1-3 show the various three-phase power supplies available in the United States of America and in Europe.
FIG. 1 illustrates the phase relationships between terminals in a three-phase power system in the United States using a “delta” configuration. As shown in FIG. 1, under the delta configuration, the phase-to-phase voltage difference between any two phases in the three-phase system is 240 volts (RMS1). FIG. 2 illustrates the phase relationships between phase terminals A, B and C in a three-phase power system in the United States using a “wye” configuration. Unlike the delta configuration, the wye configuration provides an additional terminal called the “neutral” terminal. Under the wye configuration of FIG. 2, phase-to-phase voltage between any two phase terminals is 208 volts (RMS), and the phase-to-neutral voltage between any phase terminal A, B or C and
1Root-mean square the neutral terminal is 120 volts (RMS). In most high-power equipment, however, the neutral terminal in the wye connection is rarely used. 
In Europe, the wye configuration is used extensively. FIG. 3 shows the phase relationships between terminals A, B and C in a three-phase power system in Europe using the “wye” configuration. The phase-to-phase voltage between any two phase terminals is 400 volts (RMS), nominally. (Depending on the age of the power system, the input phase-to-phase voltage may vary from 380 volts (RMS) to 415 volts (RMS)). Between any of the phase terminals A, B or C and the neutral terminal, the voltage is 230 volts (RMS).
Most modern single-phase power devices (e.g. single-phase power supplies) are designed to receive a nominal input voltage between 200-240 volts (RMS). To provide this power, a single-phase power supply used in the US has its input terminals connected to two phase terminals. However, if the same equipment is used in Europe, the same input terminals are connected to one phase terminal and the neutral terminal, respectively. This input connection can be provided by either a hardwired connection or a pluggable connection. Although a technician in the field can provide the proper hardwired connection, other local restrictions exist such that, in practice, such a connection step is not taken. A manufacturer usually provides the pluggable connection, which is typically provided within the equipment. Thus, to properly prepare a system for shipment, the manufacturer must configure the system according to where the system is intended to be used. To avoid a catastrophe, both the manufacturer and the user on location must carefully examine the connection inside the single-phase equipment for proper configuration vis a vis its power source, prior to turning on the power device. Higher reliability and lower production and installation time and cost can be avoided if such an examination is not required.